Real-time 3D Character Animation with Visual C++

Nik Lever

• Publisher: Routledge
• Year: 2001
• eBook ISBN: 9781136134777
• Topic: Computer Science
• Subtopic: Programming Games
• Index: Computer Science

Do you have some experience and a reasonable knowledge of C++ and want to write your own computer games? Have you ever looked at a PC or Playstation (R) game with characters running and leaping through an exciting landscape and wondered how it was done? If so then this book will give you all the information you need to achieve this goal, whether you are a hobby programmer, student or even a professional wanting to add that third dimension to your website. Nik Lever takes you through the journey from the basics of 3D manipulation all the way to morph objects and sub-division surfaces. On the way you get Visual C++ project files to study and software that runs on the Windows desktop. The downloadable resources give you a full-featured development environment for 3D character animation, so even if you find some of the maths and the code hard to follow straight away you can still create your own games. The game engine (Toon3DCreator) provided free and fully functional on the downloadable resources, even has an ActiveX control that allows you to distribute your work on the Internet. All source code for Toon3D is included on the downloadable resources. You will also get an insight into the artist's problems; learn how to keep the characters interesting while not exhausting the game engine. Understand the complete picture and make the most of your skills to help you succeed in, or break into the computer gaming industry with this comprehensive guide to programming for real-time 3D character animation.

1 3D basics

In this chapter we are going to introduce the 3D basics. We will look at how to store the information required for a computer to display a 3D object. In addition, we will consider the maths required to manipulate this object in 3D space and then convert this to a 2D display. We need a sufficiently general scheme that will allow us to store and manipulate the data that can be displayed as a box, a teapot or an action hero. The method generally used is to store a list of points and a list of polygons. Throughout this book, all the source code is designed to handle polygons with three or four sides.

In later chapters we will leave most low-level operations to a graphics library, which will manage most of the mathematical manipulation. In this book we use the graphics library, OpenGL. But to ease the creation of seamless mesh characters, we will need to do some of our own manipulation of point data; to understand how this code operates you will need to follow the methods outlined in this chapter.

OpenGL is the most widely adopted graphics standard

From the OpenGL website www.opengl.org

‘OpenGL is the premier environment for developing portable, interactive 2D and 3D graphics applications. Since its introduction in 1992, OpenGL has become the industry's most widely used and supported 2D and 3D graphics application programming interface (API), bringing thousands of applications to a wide variety of computer platforms. OpenGL fosters innovation and speeds application development by incorporating a broad set of rendering, texture mapping, special effects and other powerful visualization functions. Developers can leverage the power of OpenGL across all popular desktop and workstation platforms, ensuring wide application deployment.’

Describing 3D space

First let's imagine a small box lying on the floor of a simple room (Figure 1.1).

How can we create a dataset that describes the position of the box? One method is to use a tape measure to find out the distance of the box from each wall. But which wall? We need to have a frame of reference to work from.

Figure 1.2 shows the same room, only this time there are three perpendicular axes overlaid on the picture. The point where the three axes meet is called the origin. The use of these three axes allows you as a programmer to specify any position in the room using three numerical values.

Figure 1.1 A simplified room showing a small box.

Figure 1.2 A simplified room with overlaid axes.

In Figure 1.2, the two marked lines perpendicular to the axes give an indication of the scale we intend to use. Each slash on these lines represents 10 cm. Counting the slashes gives the box as 6 along the x-axis and 8 along the z-axis. The box is lying on the floor, so the value along the y-axis is 0. To define the position of the box with respect to the frame of reference we use a vector,

[6, 0, 8]

In this book, all vectors are of the form [x, y, z].

The direction of the axes is the scheme used throughout this book. The y-axis points up, the x-axis points to the right and the z-axis points out of the screen. We use this scheme because it is the same as that used by the OpenGL graphics library.

Transforming the box

To move the box around the room we can create a vector that gives the distance in the x, y and z directions that you intend to move the box. That is, if we want to move the box 60 cm to the right, 30 cm up and 20 cm towards the back wall, then we can use the vector [6, 3, 2] (recall that the scale for each dash is 10 cm) to move the box. The sum of two vectors is the sum of the components.

[x, y, z]=[x1, y1, z1] + [x2, y2, z2]

where x = x1 + x2, y = y1 + y2 and z = z1 + z2

For example, [12, 3, 10] = [6, 0, 8] + [6, 3, 2]

Describing an object

The simplest shape that has some volume has just four points or vertices. A tetrahedron is a pyramid with a triangular base. We can extend the idea of a point in 3D space to define the four vertices needed to describe a tetrahedron. Before we can draw an object we also need to define how to join the vertices. This leads to two lists: a list of vertices and a list of faces or polygons.

The vertices used are:

A: [ 0.0, 1.7, 0.0]
B: [–1.0, 0.0, 0.6]
C: [ 0.0, 0.0, –1.1]
D: [ 1.0, 0.0, 0.6]

To describe the faces we give a list of the vertices that the face shares:

1: A,B,D

2: A,D,C

3: A,C,B

4: B,C,D

Figure 1.3 A tetrahedron.

Although the triangles ABD and ADB appear to be the same, the order of ...

Table of contents

• Front Cover
• Half Title
• Dedication
• Title Page
• Copyright
• Contents at a glance
• Supplementary Resources Disclaimer
• About the author
• Introduction
• Chapter 1: 3D basics
• Chapter 2: Drawing points and polygons the hard way
• Chapter 3: Drawing points and polygons the easy way with OpenGL
• Chapter 4: OpenGL lighting and textures
• Chapter 5: Creating low polygon characters
• Chapter 6: Texture mapping
• Chapter 7: Setting up a single mesh character
• Chapter 8: Keyframe animation
• Chapter 9: Inverse kinematics
• Chapter 10: Importing geometry and animation from Lightwave 3D
• Chapter 11: Importing geometry and animation from 3DS Max
• Chapter 12: Motion capture techniques
• Chapter 13: Collision detection
• Chapter 14: Using morph objects
• Chapter 15: Using subdivision surfaces
• Chapter 16: Using multi-resolution meshes
• Chapter 17: The scene graph
• Chapter 18: Web 3D, compression and streaming
• Appendix A: Using Toon3D Creator
• Appendix B: MFC Document/View architecture – a short introduction
• Appendix C: Further information
• Index